Viral correlates of protection and the multifarious interactions of B and T cells.

Validated, reproducible methods to assess immunity to a specific virus following either infection or vaccination are important for understanding susceptibility to existing and emerging infectious diseases. Correlates of protection for a specific viral illness involve humoral and cellular responses that differ by pathogen and by the portal of entry into the host. Contemporary understanding of a correlate of protection primarily is based on serum neutralizing antibody concentrations because of difficulty in assaying the complex interactions of T cells. A more comprehensive understanding of susceptibility and protection is needed. The goal of this paper is to enumerate the multiple variables that complicate understanding of cellular contributions to the innate and adaptive immune responses.